Transition metal ions () incorporated within the cavities of zeolites by an ion-exchange method show an efficient and unique photocatalytic peformance for the decomposition of NO into N₂and O₂at 275 K. In situ ESR, UV-VIS, photoluminescence and XAFS (XANES and FT-EXAFS) investigations revealed that the transition metal ions exist in highly dispersed state with linear 2 coordination sphere within the pores of zeolites, the local structures of the metal ions being significantly affected by changing the kinds of zeolites. Detailed studies of the interaction of NO with the excited states of these metal ions clearly indicated that unique inner shell type excitation states of these metal ions play a significant role in the photocatalytic decomposition of NO, i.e., an electron transfer from the s orbital of the excited state of ions into the antibonding orbital of NO intiates the decomposition reaction of NO.